Hey, a fellow at FullSizeChevy (where Im a member) told me to come over here for some TBI help. Hope yall can help.

I've had this intermittent problem for a few years now where my passenger side injector just randomly quits, and seemingly only after I pay $75 to tow it will it mysteriously run fine again. I have swapped the ECM to no avail, and the injectors are new. I have also rewired said injector all the way back to the computer and added a new hot wire for it.

Ideas?

If I cant figure this out I have an expensive road ahead of me on a carb swap.

Thanks.

 

Like I always say, I am a n00b at this but....

Have you tried cleaning out the fuel passages all the way from the fuel line to the injectors?

Maybe somewhere between where the fuel is all one, and it splits off to go to the injectors, there is a piece of gum or varnish that will move into position and block the flow of gasoline?

On another note, what happens when an injector stops? Will the motor still run at all? I would guess it would be able to run with only 4 cylinders. I used to have a v6, and when the plug wires went bad, it would run on 2 cly, but not climb hills.

 

The passages in the throttle body? Who knows. Suggestions on cleaners?

It will run on the 3 cylinders on the left bank. Basically I can limp it off the road but it wont idle, just shudder really hard and die.

 

miles on vehicle? might be a decent idea to rebuild TBI (not as intimidating as it sounds). Took me about an hour on my bench (once it's off), with absolutely no directions, just a picture of a blown apart diagram showing and numbering the parts of the kit, and that was my first experience with a TBI so. Not terribly hard, easily clean it top to bottom. Remember to remove electronics such as the throttle position sensor and such first as to not harm it, otherwise you can use carb cleaner and a brass bristle brush, and if it's off the car then you don't have to worry about all the gunk falling in the engine. Otherwise run a bottle of injector cleaner and then i would suggest a fuel pressure test, of which if this is an intermittent problem, it may be hard to diagnose until the truck wants to do it again...but you may have weak fuel pressure of which won't let the injectors operate optimally.
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another curiosity, does this vehicle have an EGR? if that is all gunked up and clocked up, it may choke the engine (so i've read, may be wrong). Of which if thats the case that it's all gunked up like mine was, then you need to remove the intake off the engine and again, carb cleaner, brass bristle brush, and a screw driver should take care of it pretty nicely. You haven't said what size engine we're talking about...4.3L or + so i'm just throwing a couple of ideas that you possibly might want to check or others may want to ellaborate on the feasibility of my ideas.

I may be entirely wrong but it's just a couple ideas. As far as the cleaner, carb cleaner worked just fine for me.

 

Its a 4.3L with between 125,000-150,000 miles. Speedo doesnt work sometimes, and when it doesnt work, the odo doesnt and this has all been since before I owned it.

I had a guy who looked at it once take the throttle body off and give it a once over. The pressure regulator is also new. I replaced the EGR once when it acted up and threw a code, never gave issue again. It also has a new TPS and MAP sensor. Distributor, too...

I almost think it has to be something electronic perhaps, but I have no idea what info the computer receives that would influence the injector.

 

have you checked your speedo cable if so equipped? if not the vehicle speed sensor/buffer if so equiped on that speedo issue? Like i said, you probably want to check fuel pressure to at least rule that out, if there is good pressure, than you can at least rule out fuel tank to the input line of the TBI.

computer receives signals from all sorts of things from distributor, ignition coil, timing, air flow, exhaust flow. Air intake/exhuast would affect fuel (lean/rich). The vehicle is throwing absolutely no codes? Have you checked with a machine to make sure that the bulb may just be blown? Any modifications to the engine such as open element air cleaner, different/chopped exhaust, anything special about ignition system? Just a couple more ideas.

 

Oh, forgot to mention, it has a new fuel pump. It went out one day (obviously, lol).

I think it is actually a problem within the cluster.

I just checked the codes using the pin jump trick, none. Light works fine. It has been scanned with a scanner though...

Factory air cleaner, the little metal valve in it is gone though and I dont have that cheap little 'hose' that goes down to the manifold heat shroud. It has a Flow 40 with a gutted cat. Ignition is original (does have a new coil).

Edit: What the hey, since we're talking about it, here is a (terrible) picture...

 

sounds like you should of went with a 305

 

Well it will be just fine soon enough. All the parts for a carb swap will be here by Friday.

 

Sounds like you're moving on but I thought I'd mention one thing... try switching the leads for each injector and see if the other one stops working. At least then you'll know if it's physical or electrical...

M.

 

I had switched them before. Its an electrical problem. I wish I had the time to disect the TBI and study the problem but its my only mode of transport, so Its just going carb now. Luckily the manager at the store I work at (Home Depot) is nice enough to arrange a ride for me to work when I need it right now.

 

Just a thought, I should have thought of this before you were sent here, but.

When you replaced your computer you had to use the same chip, right?
If so I almost wonder if it could be the chip.

Also that is a good looking pic.

 

When they did the computer swap they used the ECM/Chip/etc out of a 1992 V6 truck.

Thanks. I like it, too

 

i have the EXACT same problem - did u ever fix this?